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Tran K, Deslarzes-Dubuis C, DeGlise S, Kaladji A, Yang W, Marsden AL, Lee JT. Patient-specific computational flow simulation reveals significant differences in paravisceral aortic hemodynamics between fenestrated and branched endovascular aneurysm repair. JVS Vasc Sci 2023; 5:100183. [PMID: 38314201 PMCID: PMC10832507 DOI: 10.1016/j.jvssci.2023.100183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 11/10/2023] [Indexed: 02/06/2024] Open
Abstract
Background Endovascular aneurysm repair with four-vessel fenestrated endovascular aneurysm repair (fEVAR) or branched endovascular aneurysm repair (bEVAR) currently represent the forefront of minimally invasive complex aortic aneurysm repair. This study sought to use patient-specific computational flow simulation (CFS) to assess differences in postoperative hemodynamic effects associated with fEVAR vs bEVAR. Methods Patients from two institutions who underwent four-vessel fEVAR with the Cook Zenith Fenestrated platform and bEVAR with the Jotec E-xtra Design platform were retrospectively selected. Patients in both cohorts were treated for paravisceral and extent II, II, and V thoracoabdominal aortic aneurysms. Three-dimensional finite element volume meshes were created from preoperative and postoperative computed tomography scans. Boundary conditions were adjusted for body surface area, heart rate, and blood pressure. Pulsatile flow simulations were performed with equivalent boundary conditions between preoperative and postoperative states. Postoperative changes in hemodynamic parameters were compared between the fEVAR and bEVAR groups. Results Patient-specific CFS was performed on 20 patients (10 bEVAR, 10 fEVAR) with a total of 80 target vessels (40 renal, 20 celiac, 20 superior mesenteric artery stents). bEVAR was associated with a decrease in renal artery peak flow rate (-5.2% vs +2.0%; P < .0001) and peak pressure (-3.4 vs +0.1%; P < .0001) compared with fEVAR. Almost all renal arteries treated with bEVAR had a reduction in renal artery perfusion (n = 19 [95%]), compared with 35% (n = 7) treated with fEVAR. There were no significant differences in celiac or superior mesenteric artery perfusion metrics (P = .10-.27) between groups. Time-averaged wall shear stress in the paravisceral aorta and branches also varied significantly depending on endograft configuration, with bEVAR associated with large postoperative increases in renal artery (+47.5 vs +13.5%; P = .002) and aortic time-averaged wall shear stress (+200.1% vs -31.3%; P = .001) compared with fEVAR. Streamline analysis revealed areas of hemodynamic abnormalities associated with branched renal grafts which adopt a U-shaped geometry, which may explain the observed differences in postoperative changes in renal perfusion between bEVAR and fEVAR. Conclusions bEVAR may be associated with subtle decreases in renal perfusion and a large increase in aortic wall shear stress compared with fEVAR. CFS is a novel tool for quantifying and visualizing the unique patient-specific hemodynamic effect of different complex EVAR strategies. Clinical Relevance This study used patient-specific CFS to compare postoperative hemodynamic effects of four-vessel fenestrated endovascular aneurysm repair (fEVAR) and branched endovascular aneurysm repair (bEVAR) in patients with complex aortic aneurysms. The findings indicate that bEVAR may result in subtle reductions in renal artery perfusion and a significant increase in aortic wall shear stress compared with fEVAR. These differences are clinically relevant, providing insights for clinicians choosing between these approaches. Understanding the patient-specific hemodynamic effects of complex EVAR strategies, as revealed by CFS, can aid in future personalized treatment decisions, and potentially reduce postoperative complications in aortic aneurysm repair.
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Affiliation(s)
- Kenneth Tran
- Division of Vascular Surgery, Stanford Healthcare, Stanford, CA
| | | | - Sebastien DeGlise
- Division of Vascular Surgery, Lausanne University Hospital, Lausanne, Switzerland
| | - Adrien Kaladji
- Department of Vascular Surgery, University of Rennes, Paris, France
| | - Weiguang Yang
- Department of Mechanical Engineering, Stanford University, Stanford, CA
| | - Alison L Marsden
- Department of Mechanical Engineering, Stanford University, Stanford, CA
| | - Jason T Lee
- Division of Vascular Surgery, Stanford Healthcare, Stanford, CA
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Faghih MM, Craven BA, Sharp MK. Practical implications of the erroneous treatment of exposure time in the Eulerian hemolysis power law model. Artif Organs 2023; 47:1531-1538. [PMID: 37032625 DOI: 10.1111/aor.14543] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 02/13/2023] [Accepted: 04/06/2023] [Indexed: 04/11/2023]
Abstract
BACKGROUND Eulerian and Lagrangian power-law formulations are both widely used for computational fluid dynamics (CFD) to predict flow-induced hemolysis in blood-contacting medical devices. Both are based on the same empirical power-law correlation between hemolysis and the shear stress and exposure time. In the Lagrangian approach, blood damage is predicted by tracking both the stress and exposure time along a finite number of pathlines in the domain. In the Eulerian approach, a scalar transport equation is solved for a time-linearized damage index within the entire domain. Previous analytical work has demonstrated that there is a fundamental problem with the treatment of exposure time in the Eulerian model formulation such that the only condition under which the model correctly represents the true exposure time is in a flow field with no streamwise velocity variation. However, the practical implications of this limitation have yet to be thoroughly investigated. METHODS In this study, we demonstrate the inaccuracy of Eulerian hemolysis power-law model predictions due to the erroneous treatment of exposure time by systematically considering four benchmark test cases with increasing degrees of flow acceleration: Poiseuille flow through a straight tube, inclined Couette flow, and flow through a converging tube with two different convergence ratios. RESULTS Compared with Lagrangian predictions, we show that, as flow acceleration becomes more pronounced, the resultant inaccuracy in the Eulerian predictions increases. For the inclined Couette flow case, there is a small degree of flow acceleration that yields a discrepancy in the range of 10% between Lagrangian and Eulerian predictions. For flows with a larger degree of acceleration, as occurs in the converging tube flow cases, the discrepancy is considerably larger (up to 257%). CONCLUSION The inaccuracy of hemolysis predictions due to the erroneous treatment of exposure time in the Eulerian power-law model can be significant when there is streamwise velocity variation in the flow field. These results may partially explain the extremely large variability in CFD hemolysis predictions reported in the literature between Lagrangian and Eulerian models.
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Affiliation(s)
- Mohammad M Faghih
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - Brent A Craven
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, Maryland, USA
| | - M Keith Sharp
- Department of Mechanical Engineering, University of Louisville, Louisville, Kentucky, USA
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3
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Wu P. Recent advances in the application of computational fluid dynamics in the development of rotary blood pumps. MEDICINE IN NOVEL TECHNOLOGY AND DEVICES 2022. [DOI: 10.1016/j.medntd.2022.100177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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Tran K, Feliciano KB, Yang W, Schwarz EL, Marsden AL, Dalman RL, Lee JT. Patient-specific changes in aortic hemodynamics is associated with thrombotic risk after fenestrated endovascular aneurysm repair with large diameter endografts. JVS Vasc Sci 2022; 3:219-231. [PMID: 35647564 PMCID: PMC9133635 DOI: 10.1016/j.jvssci.2022.04.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 04/06/2022] [Indexed: 12/24/2022] Open
Abstract
Background The durability of fenestrated endovascular aneurysm repair (fEVAR) has been threatened by thrombotic complications. In the present study, we used patient-specific computational fluid dynamic (CFD) simulation to investigate the effect of the endograft diameter on hemodynamics after fEVAR and explore the hypothesis that diameter-dependent alterations in aortic hemodynamics can predict for thrombotic events. Methods A single-institutional retrospective study was performed of patients who had undergone fEVAR for juxtarenal aortic aneurysms. The patients were stratified into large diameter (34-36 mm) and small diameter (24-26 mm) endograft groups. Patient-specific CFD simulations were performed using three-dimensional paravisceral aortic models created from computed tomographic images with allometrically scaled boundary conditions. Aortic time-averaged wall shear stress (TAWSS) and residence time (RT) were computed and correlated with future thrombotic complications (eg, renal stent occlusion, development of significant intraluminal graft thrombus). Results A total of 36 patients (14 with a small endograft and 22 with a large endograft) were included in the present study. The patients treated with large endografts had experienced a higher incidence of thrombotic complications compared with small endografts (45.5% vs 7.1%; P = .016). Large endografts were associated with a lower postoperative aortic TAWSS (1.45 ± 0.76 dynes/cm2 vs 3.16 ± 1.24 dynes/cm2; P < .001) and longer aortic RT (0.78 ± 0.30 second vs 0.34 ± 0.08 second; P < .001). In the large endograft group, a reduction >0.39 dynes/cm2 in aortic TAWSS demonstrated discriminatory power for thrombotic complications (area under the receiver operating characteristic curve, 0.77). An increased aortic RT of ≥0.05 second had similar accuracy for predicting thrombotic complications (area under the receiver operating characteristic curve, 0.78). The odds of thrombotic complications were significantly higher if patients had met the hemodynamic threshold changes in aortic TAWSS (odds ratio, 7.0; 95% confidence interval, 1.1-45.9) and RT (odds ratio, 8.0; 95% confidence interval, 1.13-56.8). Conclusions Patient-specific CFD simulation of fEVAR in juxtarenal aortic aneurysms demonstrated significant endograft diameter-dependent differences in aortic hemodynamics. A postoperative reduction in TAWSS and an increased RT correlated with future thrombotic events after large-diameter endograft implantation. Patient-specific simulation of hemodynamics provides a novel method for thrombotic risk stratification after fEVAR. The durability of fenestrated endovascular aneurysm repair (fEVAR) has been threatened by thrombotic complications. Using patient-specific computational flow simulation, the present retrospective study of 36 patients with juxtarenal aortic aneurysms treated with fEVAR identified several endograft diameter-dependent changes in aortic hemodynamics associated with thrombotic complications. A postoperative reduction in aortic wall shear stress and increased particle residence time correlated with the development of intraluminal graft thrombus and renal stent occlusion in patients treated with large diameter (>34 mm) endografts. These computationally estimated hemodynamic parameters could provide a novel method for patient-specific risk stratification for adverse events after fEVAR.
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Affiliation(s)
- Kenneth Tran
- Division of Vascular Surgery, Stanford University School of Medicine, Stanford, CA
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA
- Correspondence: Kenneth Tran, MD, Department of Vascular Surgery, Stanford University School of Medicine, 300 Pasteur Dr, Ste H3600, Stanford, CA 94305-5851
| | - K. Brennan Feliciano
- Department of Bioengineering, Stanford University School of Medicine, Stanford, CA
| | - Weiguang Yang
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA
| | - Erica L. Schwarz
- Department of Bioengineering, Stanford University School of Medicine, Stanford, CA
| | - Alison L. Marsden
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA
- Department of Bioengineering, Stanford University School of Medicine, Stanford, CA
- Department of Pediatrics (Cardiology), Stanford University School of Medicine, Stanford, CA
| | - Ronald L. Dalman
- Division of Vascular Surgery, Stanford University School of Medicine, Stanford, CA
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA
| | - Jason T. Lee
- Division of Vascular Surgery, Stanford University School of Medicine, Stanford, CA
- Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA
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Tran K, Yang W, Marsden A, Lee JT. Patient-specific computational flow modelling for assessing hemodynamic changes following fenestrated endovascular aneurysm repair. JVS Vasc Sci 2021; 2:53-69. [PMID: 34258601 PMCID: PMC8274562 DOI: 10.1016/j.jvssci.2020.11.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Objective This study aimed to develop an accessible patient-specific computational flow modelling pipeline for evaluating the hemodynamic performance of fenestrated endovascular aneurysm repair (fEVAR), with the hypothesis that computational flow modelling can detect aortic branch hemodynamic changes associated with fEVAR graft implantation. Methods Patients who underwent fEVAR for juxtarenal aortic aneurysms with the Cook ZFEN were retrospectively selected. Using open-source SimVascular software, preoperative and postoperative visceral aortic anatomy was manually segmented from computed tomography angiograms. Three-dimensional geometric models were then discretized into tetrahedral finite element meshes. Patient-specific pulsatile in-flow conditions were derived from known supraceliac aortic flow waveforms and adjusted for patient body surface area, average resting heart rate, and blood pressure. Outlet boundary conditions consisted of three-element Windkessel models approximated from physiologic flow splits. Rigid wall flow simulations were then performed on preoperative and postoperative models with the same inflow and outflow conditions. We used SimVascular's incompressible Navier-Stokes solver to perform blood flow simulations on a cluster using 72 cores. Results Preoperative and postoperative flow simulations were performed for 10 patients undergoing fEVAR with a total of 30 target vessels (20 renal stents, 10 mesenteric scallops). Postoperative models required a higher mean number of mesh elements to reach mesh convergence (3.2 ± 1.8 × 106 vs 2.6 ± 1.1 × 106; P = .005) with a longer mean computational time (10.3 ± 6.3 hours vs 7.8 ± 3.5 hours; P = .04) compared with preoperative models. fEVAR was associated with small but statistically significant increases in mean peak proximal aortic arterial pressure (140.3 ± 11.0 mm Hg vs 136.9 ± 8.7 mm Hg; P = .02) and peak renal artery pressure (131.6 ± 14.8 mm Hg vs 128.9 ± 11.8 mm Hg; P = .04) compared with preoperative simulations. No differences were observed in peak pressure in the celiac, superior mesenteric, or distal aortic arteries (P = .17-.96). When measuring blood flow, the only observed difference was an increase in peak renal flow rate after fEVAR (17.5 ± 3.8 mL/s vs 16.9 ± 3.5 mL/s; P = .04). fEVAR was not associated with changes in the mean pressure or the mean flow rate in the celiac, superior mesenteric, or renal arteries (P = .06-.98). Stenting of the renal arteries did not induce significant changes time-averaged wall shear stress in the proximal renal artery (23.4 ± 8.1 dynes/cm2 vs 23.2 ± 8.4 dynes/cm2; P = .98) or distal renal artery (32.7 ± 13.9 dynes/cm2 vs 29.6 ± 11.8 dynes/cm2; P = .23). In addition, computational visualization of cross-sectional velocity profiles revealed low flow disturbances associated with protrusion of renal graft fabric into the aortic lumen. Conclusions In a pilot study involving a selective cohort of patients who underwent uncomplicated fEVAR, patient-specific flow modelling was a feasible method for assessing the hemodynamic performance of various two-vessel fenestrated device configurations and revealed subtle differences in computationally derived peak branch pressure and blood flow rates. Structural changes in aortic flow geometry after fEVAR do not seem to affect computationally estimated renovisceral branch perfusion or wall shear stress adversely. Additional studies with invasive angiography or phase contrast magnetic resonance imaging are required to clinically validate these findings. (JVS–Vascular Science 2021;2:53-69.) Clinical Relevance Using a computational flow modelling for assessing the hemodynamic performance of fenestrated endovascular aneurysm repair (fEVAR), this real-world, patient-specific study included 10 participants and found that structural changes in aortic flow geometry after fEVAR did not seem to adversely impact estimated renal or visceral branch perfusion metrics (eg, peak and mean arterial pressure and flow rates) or wall shear stress. These findings overall support the ongoing clinical use of commercially available fEVAR devices for repair of juxtarenal aortic aneurysms, and provides a computational framework for future evaluation of fEVAR configurations in a preoperative or postoperative settings.
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Affiliation(s)
- Kenneth Tran
- Division of Vascular Surgery, Stanford University.,Cardiovascular Institute, Stanford University
| | - Weiguang Yang
- Department of Pediatrics (Cardiology), Stanford University
| | - Alison Marsden
- Department of Pediatrics (Cardiology), Stanford University.,Department of Bioengineering, Stanford University
| | - Jason T Lee
- Division of Vascular Surgery, Stanford University.,Cardiovascular Institute, Stanford University
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Yazdi SG, Docherty PD, Khanafer A, Jermy M, Kabaliuk N, Geoghegan PH, Williamson P. In-vitro particle image velocimetry assessment of the endovascular haemodynamic features distal of stent-grafts that are associated with development of limb occlusion. J R Soc N Z 2020. [DOI: 10.1080/03036758.2020.1826988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Sina G. Yazdi
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - Paul D. Docherty
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
- Institute of Technical Medicine, Furtwangen University, Villingen-Schwenningen, Germany
| | - Adib Khanafer
- Department of Surgery, University of Otago, Christchurch, New Zealand
| | - Mark Jermy
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - Natalia Kabaliuk
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - Patrick H. Geoghegan
- Department of Biomedical Engineering, School of Life & Health Sciences, Aston University, Birmingham, UK
- Department of Mechanical and Industrial Engineering, University of South Africa, Johannesburg, South Africa
| | - Petra Williamson
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
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7
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Computational Fluid Dynamics Modeling of Hemodynamic Parameters in the Human Diseased Aorta: A Systematic Review. Ann Vasc Surg 2020; 63:336-381. [DOI: 10.1016/j.avsg.2019.04.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 03/09/2019] [Accepted: 04/18/2019] [Indexed: 02/07/2023]
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8
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Wu P, Groß-Hardt S, Boehning F, Hsu PL. An energy-dissipation-based power-law formulation for estimating hemolysis. Biomech Model Mechanobiol 2019; 19:591-602. [DOI: 10.1007/s10237-019-01232-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 10/09/2019] [Indexed: 11/27/2022]
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9
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Wu P, Gao Q, Hsu PL. On the representation of effective stress for computing hemolysis. Biomech Model Mechanobiol 2019; 18:665-679. [DOI: 10.1007/s10237-018-01108-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 12/15/2018] [Indexed: 11/29/2022]
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Tasso P, Raptis A, Matsagkas M, Lodi Rizzini M, Gallo D, Xenos M, Morbiducci U. Abdominal aortic aneurysm endovascular repair: profiling post-implantation morphometry and hemodynamics with image-based computational fluid dynamics. J Biomech Eng 2018; 140:2682796. [PMID: 30029263 DOI: 10.1115/1.4040337] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Indexed: 11/08/2022]
Abstract
Endovascular aneurysm repair (EVAR) has disseminated rapidly as an alternative to open surgical repair for the treatment of abdominal aortic aneurysms (AAAs), because of its reduced invasiveness, low mortality and morbidity rate. The effectiveness of the endovascular devices used in EVAR is always at question as postoperative adverse events can lead to re-intervention or to a possible fatal scenario for the circulatory system. Motivated by the assessment of the risks related to thrombus formation, here the impact of two different commercial endovascular grafts on local hemodynamics is explored through 20 image-based computational hemodynamic models of EVAR-treated patients (N=10 per each endograft model). Hemodynamic features, susceptible to promote thrombus formation, such as flow separation and recirculation, are quantitatively assessed and compared with the local hemodynamics established in image-based infrarenal abdominal aortic models of healthy subjects (N=10). The hemodynamic analysis is complemented by a geometrical characterization of the EVAR-induced reshaping of the infrarenal abdominal aortic vascular region. The findings of this study indicate that: (1) the clinically observed propensity to thrombus formation in devices used in EVAR strategies can be explained in terms of local hemodynamics by means of image-based computational hemodynamics approach; (2) reportedly pro-thrombotic hemodynamic structures are strongly correlated with the geometry of the aortoiliac tract postoperatively. In perspective, our study suggests that future clinical follow up studies could include a geometric analysis of the region of the implant, monitoring shape variations that can lead to hemodynamic disturbances of clinical significance.
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Affiliation(s)
- Paola Tasso
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy
| | - Anastasios Raptis
- Laboratory for Vascular Simulations, Institute of Vascular Diseases, Ioannina 45500, Greece
| | - Miltiadis Matsagkas
- Department of Vascular Surgery, Faculty of Medicine, University of Thessaly, Larissa 41334, Greece
| | - Maurizio Lodi Rizzini
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy
| | - Diego Gallo
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy
| | - Michalis Xenos
- Department of Mathematics, University of Ioannina, Ioannina 45500, Greece
| | - Umberto Morbiducci
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino 10129, Italy
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Boersen JT, Groot Jebbink E, Van de Velde L, Versluis M, Lajoinie G, Slump CH, de Vries JPPM, Reijnen MMPJ. The Influence of Positioning of the Nellix Endovascular Aneurysm Sealing System on Suprarenal and Renal Flow: An In Vitro Study. J Endovasc Ther 2017; 24:677-687. [DOI: https:/doi.org/10.1177/1526602817719465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
Purpose: To examine the influence of device positioning and infrarenal neck diameter on flow patterns in the Nellix endovascular aneurysm sealing (EVAS) system. Methods: The transition of the aortic flow lumen into two 10-mm-diameter stents after EVAS creates a mismatched area. Flow recirculation may affect local wall shear stress (WSS) profiles and residence time associated with atherosclerosis and thrombosis. To examine these issues, 7 abdominal aortic aneurysm flow phantoms were created, including 3 unstented controls and 3 stented models with infrarenal neck diameters of 24, 28, and 32 mm. Stents were positioned within the instructions for use (IFU). Another 28-mm model was created to evaluate lower positioning of the stents outside the IFU (28-mm LP). Flow was visualized using optical particle imaging velocimetry (PIV) and quantified by time-averaged WSS (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) in the aorta at the anteroposterior (AP) midplane, lateral midplane, and renal artery AP midplane levels. Results: Flow in the aorta AP midplane was similar in all models. Vortices were observed in the stented models in the lateral midplane near the anterior and posterior walls. In the 32-mm IFU and 28-mm LP models, a steady state of vortices appeared, with varying location during a cycle. In all models, a low TAWSS (<10−2 Pa) was observed at the anterior wall of the aorta with peak OSI of 0.5 and peak RRT of 104 Pa−1. This region was more proximally located in the stented models. The 24- and 28-mm IFU models showed flow with a higher velocity at the renal artery inflow compared to controls. TAWSS in the renal artery was lower near the orifice in all models, with the largest area in the 24-mm IFU model. OSI and RRT in the renal artery were near zero for all models. Conclusion: EVAS enhances vorticity proximal to the seal zone, especially with lower positioning of the device and in larger neck diameters. Endobags just below the renal artery affect the flow profile in a minor area of this artery in 24- and 28-mm necks, while lower stent positioning does not influence the renal artery flow profile.
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Affiliation(s)
- Johannes T. Boersen
- Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands
- Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
| | - Erik Groot Jebbink
- Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | | | - Michel Versluis
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Guillaume Lajoinie
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | - Cornelius H. Slump
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
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12
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Boersen JT, Groot Jebbink E, Van de Velde L, Versluis M, Lajoinie G, Slump CH, de Vries JPPM, Reijnen MMPJ. The Influence of Positioning of the Nellix Endovascular Aneurysm Sealing System on Suprarenal and Renal Flow: An In Vitro Study. J Endovasc Ther 2017; 24:677-687. [PMID: 28689483 DOI: 10.1177/1526602817719465] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To examine the influence of device positioning and infrarenal neck diameter on flow patterns in the Nellix endovascular aneurysm sealing (EVAS) system. METHODS The transition of the aortic flow lumen into two 10-mm-diameter stents after EVAS creates a mismatched area. Flow recirculation may affect local wall shear stress (WSS) profiles and residence time associated with atherosclerosis and thrombosis. To examine these issues, 7 abdominal aortic aneurysm flow phantoms were created, including 3 unstented controls and 3 stented models with infrarenal neck diameters of 24, 28, and 32 mm. Stents were positioned within the instructions for use (IFU). Another 28-mm model was created to evaluate lower positioning of the stents outside the IFU (28-mm LP). Flow was visualized using optical particle imaging velocimetry (PIV) and quantified by time-averaged WSS (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT) in the aorta at the anteroposterior (AP) midplane, lateral midplane, and renal artery AP midplane levels. RESULTS Flow in the aorta AP midplane was similar in all models. Vortices were observed in the stented models in the lateral midplane near the anterior and posterior walls. In the 32-mm IFU and 28-mm LP models, a steady state of vortices appeared, with varying location during a cycle. In all models, a low TAWSS (<10-2 Pa) was observed at the anterior wall of the aorta with peak OSI of 0.5 and peak RRT of 104 Pa-1. This region was more proximally located in the stented models. The 24- and 28-mm IFU models showed flow with a higher velocity at the renal artery inflow compared to controls. TAWSS in the renal artery was lower near the orifice in all models, with the largest area in the 24-mm IFU model. OSI and RRT in the renal artery were near zero for all models. CONCLUSION EVAS enhances vorticity proximal to the seal zone, especially with lower positioning of the device and in larger neck diameters. Endobags just below the renal artery affect the flow profile in a minor area of this artery in 24- and 28-mm necks, while lower stent positioning does not influence the renal artery flow profile.
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Affiliation(s)
- Johannes T Boersen
- 1 Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands.,2 Department of Vascular Surgery, St Antonius Hospital, Nieuwegein, the Netherlands
| | - Erik Groot Jebbink
- 1 Department of Surgery, Rijnstate Hospital, Arnhem, the Netherlands.,3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | | | - Michel Versluis
- 3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands.,4 MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
| | - Guillaume Lajoinie
- 3 Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, the Netherlands
| | - Cornelius H Slump
- 4 MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands
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Javadzadegan A, Fulker D, Barber T. Recirculation zone length in renal artery is affected by flow spirality and renal-to-aorta flow ratio. Comput Methods Biomech Biomed Engin 2017; 20:980-990. [PMID: 28434235 DOI: 10.1080/10255842.2017.1319942] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Haemodynamic perturbations such as flow recirculation zones play a key role in progression and development of renal artery stenosis, which typically originate at the aorta-renal bifurcation. The spiral nature of aortic blood flow, division of aortic blood flow in renal artery as well as the exercise conditions have been shown to alter the haemodynamics in both positive and negative ways. This study focuses on the combinative effects of spiral component of blood flow, renal-to-aorta flow ratio and the exercise conditions on the size and distribution of recirculation zones in renal branches using computational fluid dynamics technique. Our findings show that the recirculation length was longest when the renal-to-aorta flow ratio was smallest. Spiral flow and exercise conditions were found to be effective in reducing the recirculation length in particular in small renal-to-aorta flow ratios. These results support the hypothesis that in renal arteries with small flow ratios where a stenosis is already developed an artificially induced spiral flow within the aorta may decelerate the progression of stenosis and thereby help preserve kidney function.
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Affiliation(s)
- Ashkan Javadzadegan
- a Faculty of Medicine and Health Sciences , Macquarie University , Sydney , Australia.,b ANZAC Research Institute , The University of Sydney , Sydney , Australia
| | - David Fulker
- c School of Mechanical and Manufacturing Engineering, The University of New South Wales , Australia
| | - Tracie Barber
- c School of Mechanical and Manufacturing Engineering, The University of New South Wales , Australia
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Boersen JT, Groot Jebbink E, Versluis M, Slump CH, Ku DN, de Vries JPPM, Reijnen MMPJ. Flow and wall shear stress characterization after endovascular aneurysm repair and endovascular aneurysm sealing in an infrarenal aneurysm model. J Vasc Surg 2017; 66:1844-1853. [PMID: 28285931 DOI: 10.1016/j.jvs.2016.10.077] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 10/10/2016] [Indexed: 11/17/2022]
Abstract
BACKGROUND Endovascular aneurysm repair (EVAR) with a modular endograft has become the preferred treatment for abdominal aortic aneurysms. A novel concept is endovascular aneurysm sealing (EVAS), consisting of dual endoframes surrounded by polymer-filled endobags. This dual-lumen configuration is different from a bifurcation with a tapered trajectory of the flow lumen into the two limbs and may induce unfavorable flow conditions. These include low and oscillatory wall shear stress (WSS), linked to atherosclerosis, and high shear rates that may result in thrombosis. An in vitro study was performed to assess the impact of EVAR and EVAS on flow patterns and WSS. METHODS Four abdominal aortic aneurysm phantoms were constructed, including three stented models, to study the influence of the flow divider on flow (Endurant [Medtronic, Minneapolis, Minn], AFX [Endologix, Irvine, Calif], and Nellix [Endologix]). Experimental models were tested under physiologic resting conditions, and flow was visualized with laser particle imaging velocimetry, quantified by shear rate, WSS, and oscillatory shear index (OSI) in the suprarenal aorta, renal artery (RA), and common iliac artery. RESULTS WSS and OSI were comparable for all models in the suprarenal aorta. The RA flow profile in the EVAR models was comparable to the control, but a region of lower WSS was observed on the caudal wall compared with the control. The EVAS model showed a stronger jet flow with a higher shear rate in some regions compared with the other models. Small regions of low WSS and high OSI were found near the distal end of all stents in the common iliac artery compared with the control. Maximum shear rates in each region of interest were well below the pathologic threshold for acute thrombosis. CONCLUSIONS The different stent designs do not influence suprarenal flow. Lower WSS is observed in the caudal wall of the RA after EVAR and a higher shear rate after EVAS. All stented models have a small region of low WSS and high OSI near the distal outflow of the stents.
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Affiliation(s)
- Johannes T Boersen
- Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands.
| | - Erik Groot Jebbink
- Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands
| | - Michel Versluis
- Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands
| | - Cornelis H Slump
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - David N Ku
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Ga
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Faghih MM, Keith Sharp M. Extending the Power-Law Hemolysis Model to Complex Flows. J Biomech Eng 2016; 138:2556264. [DOI: 10.1115/1.4034786] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2016] [Indexed: 11/08/2022]
Abstract
Hemolysis (damage to red blood cells) is a long-standing problem in blood contacting devices, and its prediction has been the goal of considerable research. The most popular model relating hemolysis to fluid stresses is the power-law model, which was developed from experiments in pure shear only. In the absence of better data, this model has been extended to more complex flows by replacing the shear stress in the power-law equation with a von Mises-like scalar stress. While the validity of the scalar stress also remains to be confirmed, inconsistencies exist in its application, in particular, two forms that vary by a factor of 2 have been used. This article will clarify the proper extension of the power law to complex flows in a way that maintains correct results in the limit of pure shear.
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Affiliation(s)
- Mohammad M. Faghih
- Biofluid Mechanics Laboratory, Department of Mechanical Engineering, University of Louisville, Louisville, KY 40292
| | - M. Keith Sharp
- Biofluid Mechanics Laboratory, Department of Mechanical Engineering, University of Louisville, Louisville, KY 40292
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Javadzadegan A, Simmons A, Barber T. Spiral blood flow in aorta-renal bifurcation models. Comput Methods Biomech Biomed Engin 2015; 19:964-76. [PMID: 26414530 DOI: 10.1080/10255842.2015.1082552] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries.
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Affiliation(s)
| | - Anne Simmons
- b School of Mechanical and Manufacturing Engineering , The University of New South Wales , Sydney , Australia
| | - Tracie Barber
- b School of Mechanical and Manufacturing Engineering , The University of New South Wales , Sydney , Australia
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Trias M, Arbona A, Massó J, Miñano B, Bona C. FDA's nozzle numerical simulation challenge: non-Newtonian fluid effects and blood damage. PLoS One 2014; 9:e92638. [PMID: 24667931 PMCID: PMC3965442 DOI: 10.1371/journal.pone.0092638] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 02/25/2014] [Indexed: 11/18/2022] Open
Abstract
Data from FDA's nozzle challenge-a study to assess the suitability of simulating fluid flow in an idealized medical device-is used to validate the simulations obtained from a numerical, finite-differences code. Various physiological indicators are computed and compared with experimental data from three different laboratories, getting a very good agreement. Special care is taken with the derivation of blood damage (hemolysis). The paper is focused on the laminar regime, in order to investigate non-Newtonian effects (non-constant fluid viscosity). The code can deal with these effects with just a small extra computational cost, improving Newtonian estimations up to a ten percent. The relevance of non-Newtonian effects for hemolysis parameters is discussed.
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Affiliation(s)
- Miquel Trias
- The Institute of Applied Computing & Community Code (IAC), University of the Balearic Islands, Palma, Spain
| | - Antonio Arbona
- The Institute of Applied Computing & Community Code (IAC), University of the Balearic Islands, Palma, Spain
- * E-mail:
| | - Joan Massó
- The Institute of Applied Computing & Community Code (IAC), University of the Balearic Islands, Palma, Spain
| | - Borja Miñano
- The Institute of Applied Computing & Community Code (IAC), University of the Balearic Islands, Palma, Spain
| | - Carles Bona
- The Institute of Applied Computing & Community Code (IAC), University of the Balearic Islands, Palma, Spain
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